Few dinosaurs are as aptly named as Apatosaurus, a sauropod whose name means “deceptive lizard.” This enormous Jurassic dinosaur deceived paleontologists for years, appearing as both Brontosaurus (“thunder lizard”) and Apatosaurus. Othniel Charles Marsh in 1877 identified Apatosaurus and, two years later, identified another Apatosaurus fossil as Brontosaurus.
It was not until 1903 that another paleontologist examined both fossils and decided they were the same genus, but different species. Unfortunately, word did not spread fast enough, so when a 1905 mounting of an Apatosaurus was done by a museum, it was labeled “Brontosaurus,” and the erroneous name spread faster than the truth.
The public loved “Brontosaurus,” simply because Apatosaurus was a gigantic dinosaur. No existing animal could come close to Apatosaurus’ impressive size: 27 meters long, 15 meters high at the shoulders, and weighing more than 30,000 kilograms (kg). If a child is asked to draw a dinosaur, Apatosaurus is the one most likely to emerge from the crayon, if only because it is easily drawn: boxy head, long neck, barrel body and long tail.
That 1905 error, though, has perpetuated many mistakes. The gentle, plant-eating Apatosaurus had a long, sloping head, not a boxy, cartoon-like skull. Its nostrils were on top of its head, not on the front of its snout. It did not have a sinuous, writhing neck; most likely it held its neck straight out or slightly raised, using its tail in an almost sail-like upward posture for counterbalance. It did not drag its tail on the ground.
Since its neck probably was not as flexible as earlier depicted, it would have been a bulk browser, but not in the stereotypical steamy swamps depicted in early movies, swinging its massive neck from treetop to water level while submerged in fetid lakes and wetlands. As a Jurassic herbivore, living 154 million to 145 million years ago, Apatosaurus had few defenses against the carnivores such as Allosaurus that roamed the area that is now the Western United States (Colorado, Wyoming, Oklahoma). This led some scientists to imagine the animal spent much of its time in the water, essentially hiding out in deep lakes to avoid being eaten. Further study has changed this thinking, showing once again the deceptive nature of Apatosaurus. The fossil record of the ecosystem in which Apatosaurus fossils are found indicates relatively dry, flat scrubland, with a few wooded areas.
No deep lakes beckoned Apatosaurus; it was too busy browsing low- to medium-height vegetation, leaving the taller plants for other herbivores, rending leaves and fibrous plants to swallow whole. Its most useful defense was its size, because a carnivore such as Saurophaganax could not easily bring down a 30,000-kg to 34,500-kg (33 to 38 tons) animal. No, Jurassic carnivores would have dined on smaller, more easily obtainable prey. That size was vital to survival is supported by the fast growth of juvenile Apatosaurus, which grew to adult size in roughly 10 years.
Adult size is difficult to imagine—Apatosaurus was as long as three school buses, and as tall as a five-story building. To keep such bulk nourished required a constant and huge intake of plant matter. Apatosaurus, like birds today, swallowed stones to grind its food in its digestive tract.
For taxonomic purposes, Apatosaurus is classified as Animalia, Chordata, Reptilia, Dinosauria, Saurischia, Sauropodomorpha, Sauropoda, Diplodocidae, Apatosaurinae, with the various species named A. ajax, A. excelsus, and A. louisae.